1. Field of the Invention
The present invention concerns a method and device for the rapid depositing of oxydes in thin layers which adhere well to plastic supports.
2. Description of the Prior Art
It is known that there are several methods making it possible to deposit thin layers on a substrate. One of the best known methods, providing very adhesive layers is cathode sputtering. Nevertheless, the depositing speed is very slow, since it reaches about a hundredth of a micron per minute in the best cases and it is not possible to adapt that method to really industrial applications for large mass-producing operations. Another method which is also well-known consists in forming deposits by evaporation of the material to be deposited. That method makes it possible to operate at a very much higher depositing speed, but the layers thus deposited on the plastic support only very rarely give the user satisfaction.
The present invention aims at developing and applying a method, recently perfected, consisting in forming with the oxide to be sprayed, a plasma in an arc state and in spraying it onto the substrate kept in a vacuum.
Layers having excellent quality are thus obtained at a depositing speed 50 to 100 times higher than with cathode sputtering. It is known that according to that recent method, the discharge in an arc medium is induced within a cavity whose walls are lined with the material to be deposited. That cavity is drilled with an opening putting it into communication with the enclosure containing the substrate. When the arc medium is established, the particles of the material to be deposited are driven out of the cavity through the opening formed in the latter, penetrate in the enclosure where a lower pressure than in the cavity prevails, and come into contact with the substrate and are deposited thereon.
It is known that the discharge is an arc state thus set up has a tendency to increase in intensity if the latter is not controlled.